(1) Field of the Invention
This invention relates to a slip roller for use in powered roller conveyors and more particularly to an improved slip roller which provides an accumulating function to a powered roller conveyor assembly.
(2) Description of the Prior Art
There are a number of slip type rollers which are described in the patent literature. Examples may be found in U.S. Pat. Nos. 4,006,815, 4,096,942 and 2,976,981. Additionally, co-pending application Ser. No. 912,676, assigned to the same assignee as the instant invention, describes a slip-type roller. U.S. Pat. Nos. 2,976,981 and 4,006,815 and application Ser. No. 912,676 have slipping characteristics which occur when the "counter-torque" (caused by an impediment to further movement of articles carried by the conveyor) becomes greater than the driving torque of the roller. Actual slippage occurs between the roller sleeve and a hub member contacting the sleeve. This prevents damage to the articles due to the pressure which otherwise would result from the driving torque. A disadvantage to this type of slip-roller assembly may occur with heavy loads. The frictional force between sleeve and hub becomes greater with increasing loads, thus increasing the driving torque. Slippage will occur with heavy loads only with greater counter-torque. This may be a serious problem, particularly with fragile but heavy articles since the pressures on the articles caused by their weight may be directly responsible for damage.
A variation of the slip-roller is described in U.S. Pat. No. 4,096,942. The drive which is an endless drive means engages a slip collar about a roller. The roller itself is supported for rotation by means independent of the slip collar. Thus, the slip collar is not affected by increasing loads and the driving torque remains essentially constant. There is, however, relative movement between the roller sleeve and slip collar which inevitably results in some wear to the sleeve.
It is, therefore, a paramount object of the present invention to provide for an improved slip-type roller which provides a constant driving torque to articles being carried by a powered roller conveyor assembly.
It is another important object of the present invention to provide a slip-type function to a roller without concurrent wear to the roller itself.
Still another important object of the present invention is to provide an improved slip-type roller which permits a conveyor assembly to have zones for accumulating articles.